CN113461857B

CN113461857B - Low cis polybutadiene rubber and preparation method thereof, HIPS and preparation method thereof

Info

Publication number: CN113461857B
Application number: CN202010244096.1A
Authority: CN
Inventors: 李建成; 刘天鹤; 鲁文平; 王雪
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2024-11-19
Anticipated expiration: 2040-03-31
Also published as: CN113461857A

Abstract

本发明涉及HIPS树脂领域，公开了一种低顺式聚丁二烯橡胶及其制备方法和HIPS树脂及其制备方法。该低顺式聚丁二烯橡胶中1,2‑聚合结构单元的含量为8‑20重量％；数均分子量为70,000‑90,000g/mol；分子量分布系数为2.25‑2.65；在100℃时的门尼粘度ML₁₊₄为40‑60；在25℃时的5重量％的苯乙烯溶液的粘度为40‑66cp。该低顺式聚丁二烯橡胶作为增韧剂，能够获得抗冲性能和光泽度更均衡的HIPS树脂。The invention relates to the field of HIPS resins, and discloses a low-cis polybutadiene rubber and a preparation method thereof, and a HIPS resin and a preparation method thereof. The low-cis polybutadiene rubber has a 1,2-polymerization structural unit content of 8-20% by weight, a number average molecular weight of 70,000-90,000 g/mol, a molecular weight distribution coefficient of 2.25-2.65, a Mooney viscosity ML ₁₊₄ at 100° C. of 40-60, and a viscosity of a 5% by weight styrene solution at 25° C. of 40-66 cp. The low-cis polybutadiene rubber is used as a toughening agent to obtain a HIPS resin with more balanced impact resistance and glossiness.

Description

Low cis-polybutadiene rubber and preparation method thereof, HIPS and preparation method thereof

Technical Field

The invention relates to the field of synthetic rubber and resin, in particular to low cis-polybutadiene rubber and a preparation method thereof, HIPS resin and a preparation method thereof.

Background

The use of different toughening rubbers can have a significant impact on the properties of HIPS resins. In theory, LCBR rubber, high cis polybutadiene rubber, styrene-butadiene-styrene thermoplastic elastomer, and the like are the rubber types commonly used in the continuous bulk process for preparing HIPS resins.

The crosslinked structure of the toughening rubber cannot be selected because the crosslinked rubber cannot undergo a grafting reaction. The high cis-polybutadiene rubber is adopted in the traditional bulk process, has low glass transition temperature, is easy to relax, has good impact resistance effect, has low-temperature crystallization tendency, and is not beneficial to the improvement of low-temperature toughness. For low-temperature toughness HIPS resin, LCBR is the best toughening agent because of the characteristics of moderate vinyl content, low gel content and random distribution of molecular chain cis-trans 1,4 structures.

LCBR rubber is classified into batch polymerization products and continuous polymerization products according to the process. The batch polymerization process is flexible, and after the polymerization is finished, a multi-functional group coupling agent is generally adopted for coupling reaction so as to balance the Mooney viscosity and the 5% styrene viscosity of the product. The continuous polymerization process cannot introduce a terminating coupling agent during the polymerization process when there is only one reactor because of the continuous material transport, otherwise the living chain is terminated by the coupling agent, and an ideal branched polymerization product is not obtained.

The commercial continuous polymerization products fall into two categories, namely single reactor continuous polymerization processes and three reactor continuous polymerization processes. The former is represented by the japanese Asahi chemical company, and the product is a linear structure without adding any branching agent during polymerization, and it is not possible to achieve a balance between the Mooney viscosity and the 5% styrene solution viscosity, and it is difficult to balance the gloss and impact properties at the same time at the time of HIPS modification. The latter is represented by Arman's company, where the polymerization is carried out in a first reactor, the coupling is carried out in a second reactor, and the termination is carried out in a third reactor; the process flow is long, the investment is large, the occupied area is large, the product adopts chlorine-containing silane as a coupling agent, and chloride ions enter the condensed water and colloidal particles in the post-treatment stage to corrode post-treatment equipment.

Disclosure of Invention

The invention aims to overcome the defect that HIPS resin obtained by toughening low cis-polybutadiene rubber prepared by a single reactor continuous polymerization process in the prior art is difficult to obtain HIPS resin with more balanced glossiness and impact resistance, and provides continuous star-shaped low cis-polybutadiene rubber serving as a toughening agent, a preparation method thereof, HIPS resin and a preparation method thereof, wherein HIPS resin with more balanced glossiness and impact resistance can be obtained.

In order to achieve the above object, the first aspect of the present invention provides a low cis-polybutadiene rubber, wherein the content of 1, 2-polymerized structural units in the low cis-polybutadiene rubber is 8 to 20% by weight; a number average molecular weight of 70,000 to 90,000g/mol; the molecular weight distribution coefficient is 2.25-2.65; the Mooney viscosity ML ₁₊₄ at 100deg.C is 40-60; the viscosity of the 5 wt% styrene solution at 25℃is 40-66cp.

The second aspect of the present invention provides a process for producing the above-mentioned low cis-polybutadiene rubber, wherein the process comprises:

(1) In an inert solvent, in the presence of an organolithium initiator, a gel inhibitor and a structure regulator, continuously introducing 1, 3-butadiene and a branching monomer into a reactor from the bottom of the reactor to carry out anionic solution polymerization until the conversion rate of the 1, 3-butadiene reaches more than 99%;

(2) And (3) contacting the mixture obtained in the step (1) with a terminator to carry out termination reaction.

In a third aspect, the present invention provides a method for producing HIPS resin, comprising:

(1) Providing a low cis-polybutadiene rubber solution containing the low cis-polybutadiene rubber obtained by the above method;

(2) Polymerizing styrene and a toughening agent in the presence of a free radical initiator; wherein the toughening agent contains the low cis-polybutadiene rubber solution obtained in the step (1).

A fourth aspect of the present invention provides HIPS resins prepared by the above-described methods.

The low cis-polybutadiene rubber realizes the balance control of the Mooney viscosity and the 5% styrene solution viscosity of single reactor continuous polymerization low cis-polybutadiene rubber (LCBR), and the low cis-polybutadiene rubber is used as a toughening agent of HIPS resin to ensure that the HIPS resin has more balanced glossiness and impact resistance. In particular, the viscosity of the 5wt% styrene solution of the low cis-polybutadiene rubber provided by the invention at 25 ℃ is below 66cp, and the HIPS resin obtained by the invention has higher glossiness.

According to the preparation method of the low cis-polybutadiene rubber, provided by the invention, the branching monomer is added from the bottom of the reaction vessel and is copolymerized with 1, 3-butadiene to prepare the star polymer, so that the correlation between the Mooney viscosity of the rubber and the viscosity of a 5 wt% styrene solution at 25 ℃ is balanced, the problem that the impact resistance and glossiness of HIPS resin prepared from the low cis-polybutadiene rubber (LCBR) prepared by a single-reactor continuous polymerization process cannot be both achieved is solved, meanwhile, the process is free of halogenation, and the corrosion problem in the preparation process is solved.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

According to a first aspect of the present invention, there is provided a low cis-polybutadiene rubber, wherein the content of 1, 2-polymerized structural units in the low cis-polybutadiene rubber is 8 to 20% by weight; a number average molecular weight of 70,000 to 90,000; the molecular weight distribution coefficient is 2.25-2.65; the Mooney viscosity ML ₁₊₄ at 100deg.C is 40-60; the viscosity of the 5 wt% styrene solution at 25℃is 40-66cp.

In the present invention, the butadiene monomer forming the low cis-polybutadiene rubber mainly refers to 1, 3-butadiene unless otherwise specified. Wherein the polymeric form of 1, 3-butadiene generally comprises a1, 2-polymeric form, thereby forming said 1, 2-polymeric structural unit (- [ CH ₂-CH₂(CH＝CH₂) ] (-), and further comprises a1, 4-polymeric form, thereby forming a1, 4-polymeric structural unit (- [ CH ₂-CH＝CH-CH₂ ] -). Wherein the content of the 1, 2-polymeric structural unit is 8 to 20 wt%, so that grafting reaction of the continuous bulk HIPS resin can be ensured. When the content of the 1, 2-polymeric structural unit is less than 8% by weight, the progress of the subsequent grafting reaction in the preparation of the post HIPS resin will be adversely affected; when the content of the 1, 2-polymeric structural unit is more than 20% by weight, crosslinking points are easily formed, which is disadvantageous in improving impact resistance. Preferably, the content of 1, 2-polymeric structural units in the low cis polybutadiene rubber is 9 to 18 wt%, more preferably 10 to 16 wt%.

In the case where the content range of the above-mentioned 1, 2-polymerized structural unit is satisfied, the content of the cis 1, 4-polymerized structural unit is preferably 20 to 40% by weight, more preferably 25 to 40% by weight, still more preferably 30 to 40% by weight; the content of trans-1, 4-polymeric structural units is preferably 40 to 60% by weight, more preferably 45 to 60% by weight, still more preferably 50 to 60% by weight.

According to the present invention, the low cis polybutadiene rubber is 70,000 to 90,000g/mol, which is set for the purpose of controlling the Mooney viscosity and the viscosity of a 5wt% styrene solution to be kept in a proper range to better balance the correlation between the Mooney viscosity and the viscosity of a 5wt% styrene solution; when the number average molecular weight of the low cis-polybutadiene rubber is less than 70,000g/mol, the requirement of Mooney viscosity of the low cis-polybutadiene rubber cannot be met, the processability of the low cis-polybutadiene rubber is poor, and the impact strength of HIPS resin is poor; when the number average molecular weight of the low cis-polybutadiene rubber is more than 90,000g/mol, the requirement of the product for the viscosity of the 5% styrene solution of the low cis-polybutadiene rubber cannot be satisfied, and the gloss of HIPS resin is poor. Preferably, the low cis-polybutadiene rubber has a number average molecular weight of 73,000 to 88,000g/mol, more preferably 75,000 to 85,000g/mol.

The low cis polybutadiene rubber of the present invention has a suitable molecular weight distribution coefficient, which facilitates control of the relative proportions of branched rubber and linear rubber to balance the relationship of Mooney viscosity and 5% styrene solution viscosity. When the molecular weight distribution coefficient of the low cis-polybutadiene rubber is less than 2.25, the branching of the product is insufficient, and the linear product occupies a relatively large amount, thereby resulting in a low Mooney viscosity of the low cis-polybutadiene rubber; when the molecular weight distribution coefficient of the low cis-polybutadiene rubber is more than 2.65, the branched product content is relatively high, and the Mooney viscosity exceeds the upper limit of the low cis-polybutadiene rubber. Preferably, the molecular weight distribution coefficient is 2.28 to 2.55, more preferably 2.3 to 2.55.

In the invention, the molecular weight and molecular weight distribution index of the low cis-polybutadiene rubber are determined by adopting a gel permeation chromatography, the gel permeation chromatography is performed by adopting an HLC-8320 gel permeation chromatograph of Tosoh corporation of Japan, chromatographic columns are TSKgel SuperMultiporeHZ-N standard columns and TSKgel SuperMultiporeHZ standard columns, a solvent is chromatographic pure Tetrahydrofuran (THF), narrow-distribution polystyrene is used as a standard sample, a polymer sample is prepared into tetrahydrofuran solution with the mass concentration of 1mg/mL, the sample injection amount is 10.00 mu L, the flow rate is 0.35mL/min, and the test temperature is 40.0 ℃.

According to the present invention, the Mooney viscosity ML ₁₊₄ at 100℃of the low cis-polybutadiene rubber of the present invention is 40-60, in order to ensure processability of the low cis-polybutadiene rubber while better balancing the gloss and impact strength of HIPS. When the Mooney viscosity ML ₁₊₄ of the low cis-polybutadiene rubber at 100 ℃ is less than 40, the processability of the low cis-polybutadiene rubber is poor, and the impact resistance of HIPS is affected; mooney viscosity ML ₁₊₄ at 100deg.C is higher than 60, and the low cis-polybutadiene rubber is easy to plasticize during the drying stage, which affects the product quality. Preferably, the low cis polybutadiene rubber has a Mooney viscosity ML ₁₊₄ at 100℃of 40-58, more preferably 45-55.

In the invention, the Mooney viscosity is measured according to GB/T1232.1 standard by adopting a GT-7080-S2 Mooney viscometer manufactured by Taiwan Gotech company, wherein the preheating time is 1min, the rotating time is 4min, and the testing temperature is 100 ℃.

According to the present invention, the low cis-polybutadiene rubber of the present invention has a viscosity of a 5 wt.% styrene solution at 25℃of 40 to 66cp, preferably 42 to 66cp, more preferably 44 to 58cp. Controlling the viscosity of a 5wt% styrene solution of a low cis-polybutadiene rubber at 25℃within the above-mentioned range and preferred range can balance the correlation between the gloss and impact resistance of the resulting HIPS resin.

The styrene solution viscosity of the 5 wt.% rubber at 25℃was determined using a Peking Yanshan petrochemical company Enterprise Standard Q/SH3155.SXL. C26-2019, and the temperature was constant at 25℃using a Fender viscometer.

According to the present invention, the low cis-polybutadiene rubber of the present invention can obtain a lower gel content, preferably, the gel content of the low cis-polybutadiene rubber is 400ppm or less, preferably 200ppm or less, more preferably 150ppm or less. The solvent system and the gel inhibitor adopted by the invention can effectively avoid accumulation of active macromolecular chains in the reactor, avoid gel generation in the polymerization stage and have extremely low gel content.

In the invention, the gel content is measured by adopting a weight method of Beijing Yanshan petrochemical industry company enterprise standard Q/SH3155.SXL.C27-2019 test. The specific process is as follows: adding the polymer sample to styrene, shaking in a shaker at 25 ℃ for 16 hours to completely dissolve the soluble matters, preparing a styrene solution containing 5 wt% of the polymer, and recording the mass of the polymer sample as C (in grams); weigh the 400 mesh clean nickel screen and record the mass of the clean nickel screen as B (in grams); then filtering the solution by using a nickel screen; washing nickel screen with styrene after filtering, drying nickel screen at 150 ℃ and normal pressure for 30 minutes, weighing, and recording the weight of the nickel screen as A (in grams); the gel content was calculated according to the following formula:

gel content% = [ (a-B)/C ] ×100%.

According to the present invention, the low cis-polybutadiene rubber of the present invention can obtain a lower color, preferably the color at a 5 wt% styrene solution of the low cis-polybutadiene rubber is less than 5, preferably 0 or less, more preferably-2 or less.

Chromaticity was measured using a Hunter desk-top color difference meter HunterLab ColorFlex, U.S. Pat. No. 3, according to the Q/SH3155.SXL. C29-2019 standard; test conditions: the color system adopts CIELAB, the optical geometry is 45 degrees/0 degrees, the light source is C light source, the observation angle is 2 degrees, and the thickness of the sample is about 15mm.

According to the present invention, the above-mentioned preparation method of the low cis-polybutadiene rubber adopts a continuous reaction mode. The process may be carried out in a reactor conventional in the art, the volume of which may be reasonably selected according to the yield of the target product and the amount of raw materials, and generally, the volume of which may be 10 to 10000L.

The inventors of the present invention have found in the study that an aromatic vinyl monomer can be copolymerized with 1, 3-butadiene as a branching monomer to prepare a star polymer, thereby balancing the rubber Mooney viscosity with the viscosity of a 5 wt% styrene solution at 25 ℃. Further, the inventors of the present invention have found that the location of the addition of the branching monomer affects the molecular weight and molecular weight distribution of the low cis-polybutadiene rubber of the final product, thereby affecting the Mooney viscosity of the product and the viscosity of a 5 wt% styrene solution at 25℃and thus affecting the impact resistance and gloss of HIPS products.

According to the invention, 1, 3-butadiene and the branching monomer are each fed continuously from the bottom of the reactor into the reactor for anionic solution polymerization. The shape of the reactor may be a shape conventional in the art, so long as the branching monomer is caused to undergo a branching reaction with 1, 3-butadiene.

According to the present invention, the inert solvent refers to an inert solvent which does not participate in the polymerization reaction, and may be a C5-C8 cycloalkane and/or a C5-C9 alkane, preferably one or more of cyclohexane, methylcyclopentane, methylcyclohexane, methylpentane, n-hexane, n-heptane and isooctane.

The amount of the inert solvent used in the present invention can be reasonably selected according to the amount of the monomer and the control requirement of the polymerization temperature, the amount of the inert solvent can be changed in a wider range, and the amount of the inert solvent can be 400-900g based on the total weight of 100g of 1, 3-butadiene monomer.

According to the invention, the inert solvent is preferably added together with the 1, 3-butadiene from the bottom of the reactor. Thereby avoiding the formation of gel due to over-concentrated local monomer concentration, ensuring the quality of LCBR rubber and further ensuring that the final HIPS product has better comprehensive performance.

According to the present invention, the organolithium initiator is not particularly limited, and various organolithium initiators conventionally used in the art for the preparation of polybutadiene rubber may be employed, preferably, the organolithium initiator is a compound represented by formula RLi, wherein R is selected from a C1-C20 alkyl group, a C6-C20 cycloalkyl group or a C6-C20 aryl group, preferably, a C1-C10 alkyl group, a C6-C8 cycloalkyl group or a C6-C8 aryl group; more preferably, the organolithium initiator is one or more of methyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, isobutyllithium, tert-butyllithium, cyclohexyllithium, 4-cyclohexylbutyllithium, phenyllithium, triphenylmethyllithium and 2-naphthyllithium, more preferably n-butyllithium and/or sec-butyllithium, still more preferably n-butyllithium, in view of the solubility and storage stability of the initiator in an inert solvent. Wherein the organic lithium initiator is added into the polymerization system in the form of a solution, and the solvent of the organic lithium initiator can be one or more of hexane, cyclohexane, heptane and the like, and the concentration is preferably 0.04-0.2 mol.L ^-1.

The amount of the initiator used in the present invention may be appropriately selected depending on the amount of the monomer used and the molecular weight of the low cis-polybutadiene rubber to be obtained, and may vary within a wide range, and preferably the molar ratio of 1, 3-butadiene to the organolithium initiator is 750 to 1300:1, preferably 850-1200:1, more preferably 900-1100:1.

According to the invention, the anionic solution polymerization is carried out in the presence of a structure modifier, the species of which may be a conventional choice in the art, preferably the structure modifier is potassium alkoxide and/or sodium alkoxide. In order to obtain a better balance between the Mooney viscosity of the low cis polybutadiene rubber and the viscosity of the 5 wt.% styrene solution, it is preferred that the structure modifier is potassium tert-pentoxy and/or potassium 2-hexanol, which has good solubility in hydrocarbon solvents.

According to the invention, the amount of the structure regulator can be reasonably selected according to various performance indexes of a target product, the amount of the structure regulator is too low, the reactivity ratio of the 1, 3-butadiene and the branched monomer is large, the branched monomer is more prone to homopolymerization, the gel is easier to produce, more gel inhibitor is needed to be added for inhibiting the gel content, and the upper limit of the addition amount of the gel inhibitor exists. The use of the structure-adjusting agent in an excessively high amount leads to easy deactivation of the molecular chain, resulting in a decrease in the conversion of 1, 3-butadiene. Preferably, the molar ratio of the amount of the structure modifier to the amount of the organolithium initiator is 0.1 to 1:1, more preferably 0.1 to 0.8:1, and still more preferably 0.1 to 0.5:1. this allows the reactivity ratio of 1, 3-butadiene to the branching monomer to be adjusted so that the 1, 3-butadiene and branching monomer are more prone to ideal copolymerization in step (2) to control the branching degree and gel content of the product without seriously inactivating the living chains.

According to the invention, the gel inhibitor is a substance which has a certain chain transfer function and can inhibit gel formation in the polymerization process, and the gel inhibitor is one or more of tetramethyl ethylenediamine/1, 2-butadiene, carbon four-raffinate and 1, 2-butadiene, preferably 1, 2-butadiene, wherein the 1, 2-butadiene can be pure substance 1, 2-butadiene or 1, 2-butadiene containing partial inert components, and can be prepared into a certain concentration according to the requirements of equipment.

According to the invention, the dosage of the gel inhibitor can be reasonably selected according to the gel content index of the target product so as to meet the requirement of the product. Preferably, the weight ratio of the gel inhibitor to 1, 3-butadiene is 1-10:10000, more preferably 5-8:10000.

According to the present invention, the anionic solution polymerization reaction in step (1) is conducted under such conditions that the conversion of 1, 3-butadiene is 99% or more. The polymerization temperature is too low, the conversion rate of the monomer in unit time is low, and the residence time needs to be prolonged; the polymerization temperature is too high, gel is easy to generate, and the quality of the product is affected.

Preferably, the conditions for the anionic solution polymerization reaction include: the temperature is 0 to 120deg.C, preferably 40 to 115deg.C (e.g., 80 to 110deg.C), and more preferably 50 to 110deg.C; the time (i.e. residence time) is 30-90min, preferably 40-80min; the gauge pressure is 0.1-2MPa, preferably 0.5-1MPa. The anionic solution polymerization reaction of the invention has higher controllability, and the polymerization temperature is easy to control, so that the performance of the obtained product is easy to control.

According to the present invention, the branching monomer is not particularly limited as long as the low cis-polybutadiene rubber of the present invention can be obtained. Preferably, the branching monomer is a C10-C16 aromatic vinyl monomer, more preferably one or more of divinylbenzene, dipropylbenzene and diallylbenzene, and even more preferably divinylbenzene. The star polymer is prepared by copolymerizing an aromatic vinyl monomer and 1, 3-butadiene, so that the relationship between the Mooney viscosity of the low cis-polybutadiene rubber and the viscosity of the 5% styrene solution is balanced, HIPS resin with more balanced glossiness and impact resistance can be obtained, meanwhile, the process is free from halogenation, and the corrosion problem in the post-treatment process is solved.

The amount of the branching monomer used in the present invention is not particularly limited as long as the low cis-polybutadiene rubber of the present invention having a number average molecular weight in the range of 70,000 to 90,000g/mol (preferably 73,000 to 88,000g/mol, more preferably 75,000 to 85,000 g/mol) and a molecular weight distribution coefficient in the range, respectively, can be produced. But in order to be able to give the resulting low cis polybutadiene rubber a more suitable branching area to give HIPS a higher impact resistance. Preferably, the molar ratio of the branching monomer to the organolithium initiator is from 0.4 to 1:1, preferably 0.4 to 0.8:1.

Wherein the branched monomer is added to the polymerization system in the form of a solution. Preferably, the solvent of the solution containing the branched monomer is chosen identically to the inert solvents mentioned before, which may be a C5-C8 cycloalkane and/or a C5-C9 alkane, preferably one or more of cyclohexane, methylcyclopentane, methylcyclohexane, methylpentane, n-hexane, n-heptane and isooctane. The concentration of the branching monomer can be adjusted within a wide range according to the metering pump range of the branching monomer.

Preferably, steps (1) and (2) are carried out in an inert atmosphere provided by an inert gas selected from one or more of nitrogen, neon and argon.

According to the present invention, in the step (2), the branching reaction can be terminated by using a terminator, and a polymerization solution of the low cis-polybutadiene rubber can be obtained.

According to the present invention, the process for producing a low cis-polybutadiene rubber of the present invention comprises a step of subjecting the mixed solution obtained in the step (2) to solvent removal in order to extract the low cis-polybutadiene rubber. The solvent removal process may be conventional in the art, for example, by vapor coagulation desolventizing to extract the low cis-polybutadiene rubber from the mixed solution.

Preferably, the terminator is one or more of C1-C4 alcohol, organic acid and carbon dioxide, preferably one or more of isopropanol, stearic acid, citric acid and carbon dioxide, more preferably carbon dioxide. Carbon dioxide is adopted for termination reaction, and can form carbonate with metal ions (Li, mg, al, fe, zn) in a polymerization system, so that the color reaction of the metal ions is avoided, and the product has lower chromaticity. The carbon dioxide may be introduced into the reaction system in the form of a gas (for example, a carbon dioxide gas having a gauge pressure of 0.2 to 1MPa (for example, may be 0.3 to 0.6 MPa)), or may be introduced into the reaction system in the form of an aqueous dry ice solution (for example, a concentration of 0.1 to 5% by weight).

The amount of carbon dioxide is not particularly limited, and the molar ratio of carbon dioxide to initiator is preferably 0.5 to 5:1, and more preferably 0.6 to 2:1. the pH value of the polymerization system can be ensured and the metal ions in the low cis-polybutadiene rubber can be removed.

In order to enable oxidation resistance of the obtained low cis-polybutadiene rubber, an antioxidant may be further incorporated into the low cis-polybutadiene rubber, preferably, after termination of step (2), an antioxidant is incorporated into the reaction system obtained by termination, whereby the resulting polymerization solution of the low cis-polybutadiene rubber may contain the antioxidant, and the solvent removal step is performed after the antioxidant is incorporated. The antioxidant is not particularly limited, and various antioxidants can be used as is conventional in the art. For example, the antioxidant is one or more of 4, 6-bis (octylthiomethyl) orthocresol (trade name: antioxidant 1520), N-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: antioxidant 1076), N- (1, 3-dimethylbutyl) -N '-phenyl-p-phenylenediamine (trade name: antioxidant 4020), N-isopropyl-N' -phenyl-p-phenylenediamine (trade name: antioxidant 4010 NA) and N-phenyl-2-naphthylamine (trade name: antioxidant D), and generally, since the antioxidant 1520 has two thioether substituents at the 2,4 positions, it has a bifunctional effect (both of a main antioxidant function and an auxiliary antioxidant function), and thus can play a role of intramolecular synergism, and the use of the antioxidant 1520 as an anti-aging system can reduce the amount of the anti-aging system. In addition, the addition of the anti-aging agent 1076 can significantly prevent breakage of the polymer molecular chain. Preferably, the combination of the anti-aging agent 1520 and the anti-aging agent 1076 is adopted, and the weight ratio of the anti-aging agent 1520 to the anti-aging agent 1076 is 0.5-5:1, more preferably, 1-3:1 and 1076 antioxidant.

Preferably, the weight ratio of the antioxidant to the amount of 1, 3-butadiene is 0.1-0.6:100, preferably 0.2-0.4:100.

The third aspect of the present invention provides a method for producing HIPS resin, wherein the method comprises:

(1) Providing a low cis-polybutadiene solution containing the low cis-polybutadiene rubber obtained by the above method;

(2) Polymerizing styrene and a toughening agent in the presence of a free radical initiator; wherein the toughening agent contains the low cis-polybutadiene solution obtained in the step (1).

According to the present invention, the solvent in the low cis-polybutadiene polymerization solution is a benzene solvent, the benzene solvent is one or more of unsubstituted or C1-C4 alkyl substituted benzene, C1-C4 alkyl can be one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, etc., and the C1-C4 alkyl substituted benzene as the benzene solvent can be single-point substituted or multi-point substituted, preferably, the benzene solvent is one or more of benzene, toluene, ethylbenzene and xylene, preferably ethylbenzene.

The benzene solvent is used in an amount such that the content of the low cis-polybutadiene rubber in the solution of the low cis-polybutadiene rubber is 25 to 55% by weight or more, and under such conditions, the benzene solvent is preferably used in an amount such that the content of butadiene is 30 to 45% by weight.

The low cis-polybutadiene solution is preferably prepared in the step (1) by forming a solution of the low cis-polybutadiene rubber and a benzene solvent. The low cis-polybutadiene rubber is obtained by removing solvent from the mixed solution obtained after the termination reaction.

According to the present invention, in the step (2) of the method for producing HIPS resin of the present invention, HIPS resin can be obtained by polymerizing a low cis-polybutadiene rubber as a toughening agent together with styrene. The toughening agent contains a solvent brought by the solution in the step (1), preferably, in the step (2), the amount of the toughening agent is such that the content of the benzene solvent is below 18 wt%, based on the total weight of the styrene and the toughening agent, and more preferably, the content of the benzene solvent is 6-18 wt%. Preferably, the weight ratio of styrene to toughening agent on a dry weight basis is 550 to 2500: 100, more preferably 600-2000:100, and even more preferably 900-1900:100.

The radical initiator may be various initiators conventionally used in the art for preparing HIPS resins according to the present invention, for example, the radical initiator may be one or more of thermal decomposition type initiators, preferably one or more selected from peroxide type initiators and azo-bis-nitrile type initiators, more preferably one or more of t-butyl peroxy-2-ethylhexyl tertiary carbonate, diacyl peroxide, peroxydicarbonate, peroxycarboxylate, alkyl peroxide and azo-bis-nitrile type compounds, still more preferably one or more of dibenzoyl peroxide, di-o-methylbenzoyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, azobisisobutyronitrile and azobisisobutyronitrile. Preferably, the weight ratio of styrene to the free radical initiator is 2500-12000:1, more preferably 3000-9500:1, more preferably 4000-9000:1, still more preferably 5000-8500:1.

According to the present invention, preferably, in the step (2), the polymerization conditions include: the polymerization conditions include: the temperature is 100-150 ℃ and the time is 7-9h. The polymerization can be carried out with stirring, for example at 100-400 rpm.

According to the present invention, in another preferred embodiment of the present invention, in step (2), the polymerization conditions include: first at 100-110℃for 1-3 hours, then at 115-125℃for 1-3 hours (e.g.1-2 hours), then at 130-140℃for 1-3 hours (e.g.1-2 hours), and finally at 145-155℃for 1-3 hours (e.g.1-2.5 hours). More preferably, in step (2), the polymerization conditions include: firstly, reacting for 1.5-2.5 hours at 105-110 ℃, then reacting for 1.5-2.5 hours at 120-125 ℃, then reacting for 1.5-2.5 hours at 130-135 ℃, and finally reacting for 1.5-2.5 hours at 150-155 ℃. The polymerization can be carried out with stirring, for example at 100-400 rpm.

The invention also provides HIPS resin prepared by the method.

Preferably, in the HIPS resin of the present invention, the content of the structural unit of styrene is 85 to 95% by weight, preferably 90 to 95% by weight (it is understood that the remaining content is mainly structural units provided by butadiene, i.e., the content of the structural unit of butadiene is 5 to 15% by weight, preferably 5 to 10% by weight), and the number average molecular weight is 60,000 to 150,000, more preferably 80,000 to 120,000; the molecular weight distribution coefficient is 2-3.

The method of the present invention enables HIPS resin products with more balanced gloss and impact properties, preferably, the HIPS resin has a cantilever impact strength of 10kJ/m ² or more, preferably 10.5kJ/m ² or more; the 60 DEG surface gloss is 70 or more, preferably 80 or more. HIPS mechanical properties were tested using the INSTRON 5567 Universal materials tester. Wherein, the notch impact strength of the cantilever beam is measured according to GB/T1843-1996 standard (kJ/m ²); 60 ° surface gloss is measured according to ASTM D526 (60 °).

The present invention will be described in detail by examples.

In the following examples and comparative examples, the measurement methods involved include:

(1) The monomer conversion is determined gravimetrically, i.e. the weight of polymer after removal of solvent, as a percentage of the theoretical polymer yield.

(2) The Mooney viscosity was measured according to GB/T1232.1 standard using a GT-7080-S2 Mooney viscometer manufactured by Taiwan Gotech, wherein the preheating time was 1min, the rotation time was 4min, and the test temperature was 100deg.C.

(3) The content of 1, 2-polymerized structural units in the low cis-polybutadiene rubber is measured by using a AVANCEDRX MHz nuclear magnetic resonance (¹ H-NMR) method produced by BRUKER, wherein the resonance frequency of a ¹ H core is 300.13MHz, the spectrum width is 2747.253Hz, the pulse width is 5.0 mu s, the data point is 16K, the diameter of a sample tube is 5mm, the solvent is deuterated chloroform CDCl ₃, the concentration of the sample is 15% (W/V), the test temperature is normal temperature, the scanning times are 16 times, and the chemical displacement of tetramethylsilane is 0ppm for calibration.

(4) Molecular weight and molecular weight distribution were determined using an HLC-8320 type gel permeation chromatograph from eastern co., japan, wherein the test conditions include: the chromatographic column is TSKgel SuperMultiporeHZ-N, the standard column is TSKgel SuperMultiporeHZ, the solvent is chromatographic pure THF, the calibration standard sample is polystyrene, the mass concentration of the sample is 1mg/ml, the sample injection amount is 10.00 mu l, the flow rate is 0.35ml/min, and the test temperature is 40.0 ℃.

(5) The styrene solution viscosity of 5 wt.% rubber at 25℃was determined using a Peking Yanshan petrochemical company, inc. Standard Q/SH3155.SXL.C26-2019, and was measured using a Fender viscometer at a constant temperature of 25 ℃.

(6) In the invention, the gel content is measured by adopting a weight method of Beijing Yanshan petrochemical industry company enterprise standard Q/SH3155.SXL.C27-2019 test. The specific process is as follows: adding the polymer sample to styrene, shaking in a shaker at 25 ℃ for 16 hours to completely dissolve the soluble matters, preparing a styrene solution containing 5 wt% of the polymer, and recording the mass of the polymer sample as C (in grams); weigh the 400 mesh clean nickel screen and record the mass of the clean nickel screen as B (in grams); then filtering the solution by using a nickel screen; washing nickel screen with styrene after filtering, drying nickel screen at 150 ℃ and normal pressure for 30 minutes, weighing, and recording the weight of the nickel screen as A (in grams); the gel content was calculated according to the following formula:

gel content% = [ (a-B)/C ] ×100%.

(7) Chromaticity was measured using a Hunter desk-top color difference meter HunterLab ColorFlex, U.S. Pat. No. 3, according to the Q/SH3155.SXL. C29-2019 standard; test conditions: the color system adopts CIELAB, the optical geometry is 45 degrees/0 degrees, the light source is C light source, the observation angle is 2 degrees, and the thickness of the sample is about 15mm.

(8) HIPS mechanical properties were tested using the INSTRON 5567 Universal materials tester. Wherein, the notch impact strength of the cantilever beam is measured according to GB/T1843-1996 standard (kJ/m ²); 60 ° surface gloss is measured according to ASTM D526 (60 °).

Experimental device and process: the experiment was carried out in a 16L polymerization reactor (custom made by Darli, internal diameter of the reactor 20 cm) with a feed mode of lower inlet and upper outlet, operating at full load. The solvent, the butadiene monomer, the branching monomer, the gel inhibitor, the initiator and the structure regulator are respectively added from the bottom of the reactor, and the terminator and the antioxidant are added into a pipeline at the outlet of the reactor to obtain the polymer glue solution.

The experimental pressures are all gauge pressures.

Antioxidant 1520 is purchased from national pharmaceutical agents; antioxidant 1076 was purchased from enokid reagent company.

Organolithium initiators were all purchased from carbofuran reagent company and diluted to 0.07 mol.L ^-1 with hexane.

1,2 Butadiene was purchased from enokaki reagent company and diluted with hexane to a1 wt% concentration.

Potassium terpentoxil was purchased from Balanocarb reagent company and diluted to 0.02 mol.L ^-1 with hexane.

Divinylbenzene (DVB) was purchased from Inonoka reagent Co and diluted to 0.04 mol.L ^-1 with hexane.

Example 1

This example is intended to illustrate the low cis-polybutadiene rubber of the present invention and its preparation method.

(1) N-hexane solvent, 1, 3-butadiene monomer, DVB monomer, 1, 2-butadiene (gel inhibitor), organolithium initiator and structure regulator (the types and the amounts are shown in Table 1, and the flow rates are all measured by pure compounds) are respectively added into a 16L reactor from the bottom of the reactor under the protection of nitrogen; and the anionic solution polymerization reaction was carried out at the specified temperature and reaction pressure (the conditions are shown in Table 1),

(2) A terminator and an antioxidant (the types and amounts are shown in Table 2, the flow rates listed in the tables are all measured as pure compounds) were sequentially added to the line at the outlet of the upper portion of the polymerization, to finally obtain a polymerization solution PB1 of a low cis-polybutadiene rubber having a low cis-polybutadiene rubber content of 15.8% by weight.

The finally obtained polymer solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer C1 were measured, the results being shown in Table 3.

Examples 2 to 5

According to the method of example 1, except that the polymerization solutions PB2 to PB5 of the low cis-polybutadiene rubbers were obtained by carrying out the reactions using the materials and amounts shown in Table 1, respectively, the contents of the respective low cis-polybutadiene rubbers were: PB2:15.8 wt.%; PB3:15.8 wt.%; PB4: 15.8 wt.%; PB5: 15.8% by weight.

The finally obtained polymer solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer C2-C5 were measured, and the results are shown in Table 3.

Example 6

According to the method of example 1, except that isopropyl alcohol was used as the terminator instead of the carbon dioxide aqueous solution and 0.15g of isopropyl alcohol was used per 100g of 1, 3-butadiene, a polymerization solution PB6 of low cis-polybutadiene rubber was obtained, in which the content of low cis-polybutadiene rubber was 15.8% by weight.

The final polymer solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer C6 were measured, and the results are shown in Table 3.

Comparative example 1

According to the method of example 1, except that DVB was not added as a comonomer at the bottom of the reactor, thereby obtaining a polymerization solution DPB1 of low cis-polybutadiene rubber, wherein the content of low cis-polybutadiene rubber was 15.7 wt%.

The final polymerization solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer DC1 were measured, and the results are shown in Table 3.

Comparative example 2

According to the method of example 1, except that the DVB flow was 1.94g/h, a polymerization solution DPB2 of low cis-polybutadiene rubber was obtained, in which the content of low cis-polybutadiene rubber was 15.8% by weight.

The final polymerization solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer DC2 were measured, and the results are shown in Table 3.

Comparative example 3

According to the method of example 1, except that the flow rate of n-butyllithium during the polymerization was 2.66g/h, thereby obtaining a polymerization solution DPB3 of low cis-polybutadiene rubber, wherein the content of low cis-polybutadiene rubber was 15.8% by weight.

The final polymerization solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer DC3 were measured, and the results are shown in Table 3.

Comparative example 4

According to the method of example 1, except that 1, 2-butadiene was not added during the polymerization, gel was hung in the polymerization vessel after 6 hours, and normal polymerization was impossible; a polymerization solution DPB4 of low cis-polybutadiene rubber was obtained, in which the content of low cis-polybutadiene rubber was 15.8% by weight.

A part of the finally obtained polymer solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the obtained polymer DC4 was subjected to structural and performance measurement, and the results are shown in Table 3.

Comparative example 5

According to the method of example 1, except that potassium t-pentoxy was not added during the polymerization, a large amount of gel was formed in the polymerization vessel after 24 hours; a polymerization solution DPB5 of low cis-polybutadiene rubber was obtained, in which the content of low cis-polybutadiene rubber was 15.8% by weight.

The finally obtained polymer solution sample was taken out and subjected to steam coagulation desolventizing treatment, and the structure and properties of the obtained polymer DC5 were measured, the results of which are shown in Table 3.

Comparative example 6

According to the method of example 1, except that the branched monomer DVB in hexane solution is continuously added to the reactor at a distance of 1/2 from the bottom of the reactor. Thus, a polymerization solution DPB6 of low cis-polybutadiene rubber was obtained, wherein the content of low cis-polybutadiene rubber was 15.7% by weight.

The polymer DC6 obtained by taking out the finally obtained polymer solution sample and subjecting it to steam coagulation desolventizing treatment was subjected to structure and property measurement, and the results are shown in Table 3.

Comparative example 7

According to the method of example 1, except that the n-hexane solution containing the branched monomer DVB was continuously fed into the reactor at a distance of 5/8 from the bottom of the reactor, thereby obtaining a polymerization solution DPB7 of low cis-polybutadiene rubber, wherein the content of the low cis-polybutadiene rubber was 15.7 wt%.

The polymer DC7 obtained by taking out the finally obtained polymer solution sample and subjecting it to steam coagulation desolventizing treatment was subjected to structure and property measurement, and the results are shown in Table 3.

TABLE 1

TABLE 2

TABLE 3 Table 3

As can be seen from Table 3, the low cis-polybutadiene rubber prepared by the invention has moderate 5% styrene solution viscosity and Mooney viscosity, low chromaticity and gel content, and is particularly suitable for being used as HIPS (or ABS) toughening agent.

Example 7

This example is illustrative of HIPS resin of the present invention and its preparation method

(1) 96G of the low cis-polybutadiene rubber C1 obtained in example 1 was mixed with 234g of ethylbenzene to form a low cis-polybutadiene polymer solution;

(2) Mixing 330g of the polymerization solution of the low cis-polybutadiene rubber obtained in the step (1) with 1100g of styrene monomer, adding 45g of mineral oil (provided by chemical industry one factory of Peking Yanshan petrochemical company, the same applies hereinafter) and 0.1g of peroxy-2-ethylhexyl tert-butyl carbonate, polymerizing for 2h at a stirring rate of 300rpm and a polymerization temperature of 105 ℃, and then heating to 120 ℃ for 2h; and (3) heating to 135 ℃ for polymerization for 2 hours under the stirring speed of 100rpm, heating to 150 ℃ for polymerization for 2 hours, and carrying out vacuum flash evaporation on the reaction product to remove unreacted monomers and solvent to obtain HIPS resin P1.

The HIPS resin was dried and then subjected to structural and performance measurements, the results of which are shown in Table 4.

Example 8

This example is a description of HIPS resin and method of preparing the same of the present invention.

(1) 90G of the low cis-polybutadiene rubber C2 obtained in example 2 was mixed with 210g of ethylbenzene to form a low cis-polybutadiene polymer solution;

(2) Mixing 300g of the polymerization solution of the low cis-polybutadiene rubber obtained in the step (1) with 1100g of styrene monomer, adding 50g of mineral oil and 0.2g of azobisisobutyronitrile, mixing, polymerizing for 1.5h at the stirring speed of 350rpm and the polymerization temperature of 110 ℃, and then heating to 120 ℃ for polymerizing for 2.5h; and (3) under the stirring speed of 200rpm, heating to 130 ℃ for polymerization for 1.5h, heating to 155 ℃ for polymerization for 2h, and carrying out vacuum flash evaporation on the reaction product to remove unreacted monomers and solvent to obtain HIPS resin P2.

Examples 9 to 12

According to the method of example 7, except that the low cis-polybutadiene rubber C3-C6 was used in place of the low cis-polybutadiene rubber C1, respectively, the reaction product was subjected to vacuum flash evaporation to remove unreacted monomers and solvent, thereby obtaining HIPS resins P3-P6, respectively.

Comparative example 6

According to the method of example 7, except that the low cis-polybutadiene rubber described in DC1 to DC5 was used in place of the low cis-polybutadiene rubber C1, respectively, the reaction product was subjected to vacuum flash evaporation to remove unreacted monomers and solvent, thereby obtaining HIPS resins DP1 to DP5, respectively.

Comparative examples 7 to 8

According to the method of example 7, except that the low cis-polybutadiene rubber described as DC6-DC7 was used in place of the low cis-polybutadiene rubber C1, respectively, the reaction product was subjected to vacuum flash evaporation to remove unreacted monomers and solvent, thereby obtaining HIPS resins DP6-DP7, respectively.

Comparative examples 9 to 10

According to the method of example 7, except that the low cis-polybutadiene rubber C1 was replaced with Japanese Asahi chemical products 720A and 730A (freed of solvent), respectively, HIPS resins DP8-DP9 were obtained.

TABLE 4 Table 4

As can be seen from Table 4, HIPS resins having more balanced impact resistance and gloss can be obtained by using the low cis-polybutadiene of the present invention as a toughening agent, and the HIPS resins obtained by the present invention have better overall properties than HIPS resins obtained by using toughening agents which are popular in the market.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A low-cis polybutadiene rubber, characterized in that the content of 1,2-polymerized structural units in the low-cis polybutadiene rubber is 8-20% by weight; the number average molecular weight is 70,000-90,000 g/mol; the molecular weight distribution coefficient is 2.25-2.65; the Mooney viscosity ML ₁₊₄ at 100° C. is 40-60; the viscosity of a 5% by weight styrene solution at 25° C. is 40-66 cp, the gel content of the low-cis polybutadiene rubber is less than 200 ppm; and the chromaticity of the 5% by weight styrene solution of the low-cis polybutadiene rubber is less than -2.

2. The low-cis polybutadiene rubber according to claim 1, wherein the content of 1,2-polymerized structural units in the low-cis polybutadiene rubber is 9-18% by weight.

3. The low-cis polybutadiene rubber according to claim 1, wherein the content of 1,2-polymerized structural units in the low-cis polybutadiene rubber is 10-16 wt%.

The low-cis polybutadiene rubber according to claim 1 , wherein the number average molecular weight is 73,000-88,000 g/mol.

The low-cis polybutadiene rubber according to claim 1 , wherein the number average molecular weight is 75,000-85,000 g/mol.

The low-cis polybutadiene rubber according to claim 1 , wherein the molecular weight distribution coefficient is 2.28-2.55.

7. The low-cis polybutadiene rubber according to claim 1, wherein the molecular weight distribution coefficient is 2.3-2.55.

8. The low-cis polybutadiene rubber according to claim 1, wherein the Mooney viscosity ML ₁₊₄ at 100°C is 40-58.

9. The low-cis polybutadiene rubber according to claim 1, wherein the Mooney viscosity ML1+4 at 100°C is 45-55.

10. The low-cis polybutadiene rubber according to claim 1, wherein the viscosity of a 5 wt% styrene solution at 25°C is 42-66 cp.

11. The low-cis polybutadiene rubber according to claim 1, wherein the viscosity of a 5 wt% styrene solution at 25°C is 44-58 cp.

12. A method for preparing the low-cis polybutadiene rubber according to any one of claims 1 to 11, wherein the method comprises:

(1) in an inert solvent, in the presence of an organic lithium initiator, a gel inhibitor and a structure regulator, 1,3-butadiene and a branched monomer are continuously introduced into a reactor from the bottom of the reactor to perform an anionic solution polymerization reaction until the conversion rate of 1,3-butadiene reaches more than 99%;

(2) contacting the mixture obtained in step (1) with a terminator to terminate the reaction,

The gel inhibitor is one or more of tetramethylethylenediamine/1,2-butadiene, C4 residue and 1,2-butadiene.

13. The preparation method according to claim 12, wherein the organic lithium initiator is a compound represented by the formula RLi, wherein R is selected from a C1-C20 alkyl group, a C6-C20 cycloalkyl group or a C6-C20 aryl group.

14. The preparation method according to claim 12, wherein the organic lithium initiator is one or more of methyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, isobutyl lithium, tert-butyl lithium, cyclohexyl lithium, 4-cyclohexylbutyl lithium, phenyl lithium, triphenylmethyl lithium and 2-naphthyl lithium.

15. The preparation method according to claim 12, wherein the organic lithium initiator is n-butyl lithium and/or sec-butyl lithium.

16 . The preparation method according to claim 12 , wherein the molar ratio of the organic lithium initiator to 1,3-butadiene is 750-1300:1.

17 . The preparation method according to claim 12 , wherein the molar ratio of the organic lithium initiator to 1,3-butadiene is 850-1200:1.

18. The preparation method according to claim 12, wherein the molar ratio of the organic lithium initiator to 1,3-butadiene is 900-1100:1.

19. The preparation method according to claim 12, wherein the inert solvent is C5-C8 cycloalkane and/or C5-C9 alkane.

20. The preparation method according to claim 12, wherein the inert solvent is one or more of cyclohexane, methylcyclopentane, methylcyclohexane, methylpentane, n-hexane, n-heptane and isooctane.

21. The method according to claim 12, wherein the conditions of the anionic solution polymerization reaction include: temperature of 0-120°C; time of 30-90 min; gauge pressure of 0.1-2 MPa.

22. The method according to claim 12, wherein the conditions of the anionic solution polymerization reaction include: temperature of 40-115°C; time of 40-80 min; gauge pressure of 0.5-1 MPa.

23. The method according to claim 12, wherein the conditions of the anionic solution polymerization reaction include: a temperature of 50-110°C.

24. The preparation method according to any one of claims 12 to 23, wherein the structure regulator is potassium alkoxide.

25. The preparation method according to any one of claims 12 to 23, wherein the structure regulator is potassium tert-pentoxide and/or potassium 2-hexoxide.

26. The preparation method according to any one of claims 12 to 23, wherein the molar ratio of the structure regulator to the initiator is 0.05-0.5:1.

27. The preparation method according to any one of claims 12 to 23, wherein the molar ratio of the structure regulator to the initiator is 0.1-0.2:1.

28. The preparation method according to any one of claims 12 to 23, wherein the weight ratio of the gel inhibitor to 1,3-butadiene is 1-10:10000.

29. The preparation method according to any one of claims 12 to 23, wherein the weight ratio of the gel inhibitor to 1,3-butadiene is 5-8:10000.

30. The preparation method according to any one of claims 12 to 23, wherein the branching monomer is a C10-C16 aromatic vinyl monomer.

31. The preparation method according to any one of claims 12 to 23, wherein the branching monomer is one or more of divinylbenzene, dipropylenebenzene and diallylbenzene.

32. The preparation method according to any one of claims 12 to 23, wherein the molar ratio of the branched monomer to the organic lithium initiator is 0.4-1:1.

33. The preparation method according to any one of claims 12 to 23, wherein the molar ratio of the branched monomer to the organic lithium initiator is 0.4-0.8:1.

34. The method according to any one of claims 12 to 23, wherein the terminator is one or more of a C1-C4 alcohol, an organic acid and carbon dioxide.

35. The method according to any one of claims 12 to 23, wherein the terminator is one or more of isopropyl alcohol, stearic acid, citric acid and carbon dioxide.

36. The method according to any one of claims 12 to 23, wherein the terminator is carbon dioxide.

37. The method according to any one of claims 12 to 23, wherein the method comprises the step of removing the solvent from the mixed solution obtained in step (2).

38. A method for preparing a HIPS resin, the method comprising:

(1) providing a low-cis polybutadiene rubber solution, wherein the low-cis polybutadiene rubber solution contains the low-cis polybutadiene rubber obtained by the method according to any one of claims 12 to 37;

(2) In the presence of a free radical initiator, polymerizing styrene and a toughening agent; wherein the toughening agent contains the low-cis polybutadiene rubber solution obtained in step (1).

39. The preparation method according to claim 38, wherein the solvent in the low-cis polybutadiene rubber solution is a benzene solvent, and the benzene solvent is one or more of unsubstituted or C1-C4 alkyl-substituted benzene.

40. The preparation method according to claim 38, wherein the amount of the benzene solvent is 6-18 wt% based on the total weight of styrene, benzene solvent and toughening agent.

41. The preparation method according to claim 38, wherein the weight ratio of styrene to toughening agent on a dry weight basis is 550-2500:100.

42. The preparation method according to claim 38, wherein the weight ratio of styrene to toughening agent on a dry weight basis is 600-2000:100.

43. The preparation method according to claim 38, wherein the weight ratio of styrene to toughening agent on a dry weight basis is 900-1900:100.

44. The preparation method according to claim 38 or 39, wherein the free radical initiator is one or more of diacyl peroxide, peroxydicarbonate, peroxycarboxylate, alkyl peroxide and azobisnitrile compounds.

45. The preparation method according to claim 38 or 39, wherein the free radical initiator is one or more of tert-butyl peroxy-2-ethylhexyl tert-butyl carbonate, dibenzoyl peroxide, di-o-toluoyl peroxide, tert-butyl perbenzoate, diisopropylbenzene peroxide, azobisisobutyronitrile and azobisisoheptylonitrile.

46. The preparation method according to claim 38 or 39, wherein the free radical initiator is one or more of dibenzoyl peroxide, di-o-methylbenzoyl peroxide, tert-butyl perbenzoate, diisopropylbenzene peroxide, azobisisobutyronitrile and azobisisoheptylonitrile.

47. The preparation method according to claim 38 or 39, wherein the weight ratio of styrene to the free radical initiator is 2500-12000:1.

48. The preparation method according to claim 38 or 39, wherein the weight ratio of styrene to the free radical initiator is 3000-9500:1.

49. The preparation method according to claim 38 or 39, wherein the weight ratio of styrene to the free radical initiator is 4000-9000:1.

50. The preparation method according to claim 38 or 39, wherein the weight ratio of styrene to the free radical initiator is 5000-8500:1.

51. The preparation method according to claim 38 or 39, wherein the polymerization reaction conditions include: temperature of 100-150°C and time of 7-9h;

Alternatively, the polymerization reaction conditions include: first reacting at 100-110° C. for 1-3 h, then reacting at 115-125° C. for 1-3 h, then reacting at 130-140° C. for 1-3 h, and finally reacting at 145-155° C. for 1-3 h.

52. The preparation method according to claim 38 or 39, wherein the conditions of the polymerization reaction include: first reacting at 105-110°C for 1.5-2.5h, then reacting at 120-125°C for 1.5-2.5h, then reacting at 130-135°C for 1.5-2.5h, and finally reacting at 150-155°C for 1.5-2.5h.

53. HIPS resin obtained by the preparation method described in any one of claims 38 to 52.

54. The HIPS resin according to claim 53, wherein the content of the structural unit of styrene in the HIPS resin is 85-95% by weight; and the number average molecular weight of the HIPS resin is 60,000-150,000.

55. The HIPS resin according to claim 53, wherein the content of the structural unit of styrene in the HIPS resin is 90-95% by weight; and the number average molecular weight of the HIPS resin is 80,000-120,000.

56. The HIPS resin according to claim 53, wherein the surface glossiness of the HIPS resin at 60° is greater than 70, and the Izod notched impact strength measured according to the GB/T 1843 method is ^greater than 10 kJ/m2.